This answer in regard to Ramban is simply wrong. Try actually looking at his commentary to Bereshit 12:6. hebrewbooks.org/pdfpager.aspx?req=9597&st=&pgnum=168 It does not cite Tanchuma explicitly. That note was likely added by by some editor. Also Ramban is late 12th to early 13th century. What's more, the Midrash Tanchuma (also called Tanchuma A and the Buber edition) is dated to the 5th century or the 8th century on the outside.
– Yaacov DeaneDec 20 '16 at 19:40

Taking this just a little further, the principle of מעשה אבות סימן לבנים is brought in several places in Bereshit Rabbah (43:3 and 52:7 in regard to Avraham, and 68:12 and 78:8 in regard to Yaacov). That is according to most views composed between the 3rd and 5th century. It is always quoting the Rabbanim.
– Yaacov DeaneDec 20 '16 at 21:43

in regard to Ramban is simply wrong. How so? ` It does not cite Tanchuma explicitly` I never said it did. Perhaps I should make this even clearer, lest anyone else misread it. is dated to the 5th century or the 8th century The dating of Tanhuma and its various variants is indeed a debated topic. How that invalidates my answer, is a mystery. | Remember that the OP asked where the particular expression comes from. I answered this, and indeed gave some extra background. I fail to see how the question has not been answered. @YaacovDeane
– mevaqeshDec 20 '16 at 21:49

If I misunderstood your answer, I apologize. It seems to be suggesting that the expression is very late, even perhaps as late as the 16th century. But the Midrash Rabbah is written by an Amora (3rd century) bringing much earlier teachings. Also, what is the @davidkenner reference? Was that supposed to be a link?
– Yaacov DeaneDec 20 '16 at 22:52

Evidently his comment was deleted. The question was about the expression; not related ideas, but the expression. If you have evidence that the answer is wrong, please indicate that. I see none in any of your comments. It all seems to be about the idea, a fascinating point in its own right. If you are interested in this point consider asking a separate question about it. Consider also not downvtoting posts that answer the OP's question, just because you think that the OP should have asked a different question. @YaacovDeane
– mevaqeshDec 20 '16 at 23:24